Toilets are often provided in vehicles, such as boats, ships and recreational vehicles, and are often used for camping or other portable purposes. It is conventional practice to flush a portable toilet by using a manually-actuated pump for pumping water or other flushing fluid into the toilet bowl. For example, bellows-style pumps are commonly used to pump the water. However, bellows-style pumps require the user to continuously actuate the pump to maintain a water flow into the toilet bowl, and often the water flow is poor and/or erratic. Some users, such as young users, elderly users, or handicapped users may experience difficulty in using a bellows style pump to maintain a continuous supply of water to the toilet bowl. Alternatively, it is also known to use a powered pump for pumping water or other flushing fluid into the toilet bowl. For example, an electric water pump may be used to pump the water. However, the use of a powered pump requires a power source that may not be available, for example, in smaller vehicles or when the toilet is used for camping. Thus, there is a need for an improved portable toilet that can avoid these problems.